Calpains are calcium--dependent cysteine proteases present in a variety of tissues and cells. Excessive activation of calpain provides a molecular link between ischaemia or injury induced by increases in intraneuronal calcium and pathological neuronal degeneration. If the elevated calcium levels are left uncontrolled, serious structural damage to neurons may result. Recent research has suggested that calpain activation may represent a final common pathway in many types of brain damage. Selective inhibition of calpain would, therefore, be an attractive therapeutic approach in the treatment of neurodegenerative diseases. Exemplary of these diseases would be myocardial ischaemia, cerebral ischaemia, muscular dystrophy, stroke, Alzheimer's disease, or traumatic brain injury. The compounds of this invention may also be useful in the treatment of cataracts and platelet aggregation.